Diagnostic Radiology
The Barium Enema: Evidence for Proper Utilization 1 Donald E. Gerson, M.D.,2 Ann M. Lewicki, M.D., M.P.H.,3 Barbara J. McNeil, M.D., Ph.D., Herbert L. Abrams, M.D., and Eric Korngold, M.A.
A group of 1,041 patients was studied inanattempt to identify symptoms, signs, or laboratory findings (disease indicators) associated with either a high or lowyield of abnormal barium enemas. A specific search was undertaken for subgroups with one or more statistically significant indicators of large bowel disease. If enemas were performed only forstatistically significant indicators (fever, positive stool benzidine, rectal or abdominal mass, low hematocrit) or indicators of clinical importance (weight loss, constipation, diarrhea, etc.) only 13% of examinations would be eliminated. At the same time, however, 10% of patients with gastrointestinal disease would be missed. INDEX TERMS: Barium enema examination, indications. Colon, diseases. (Colon, examination, 7[5].128). (Colon, routine barium enema, 7[5].1281) Radiology 130:297-301, February 1979 TABLE I: INDICATION FOR BARIUM ENEMA
HE BARIUM ENEMA is so well established and widely used that its utility in diagnostic radiology is rarely questioned. Furthermore, the indications for the examination (rectal bleeding, left lower quadrant pain, constipation, change in bowel habits, etc.) are well known and generally accepted. As a result, there have been few critical evaluations of the relationship of indications to yield (1) and cost effectiveness. The present investigation studied the yield of positive findings in barium enemas of a large group of patients. The major objective was identification of symptoms, signs, and laboratory findings which were correlated with either a high or low yield of abnormal enemas. A secondary objective was determination of the financial implications associated with use of the barium enema as a test for gastrointestinal disease when either the entire initial patient population or selected subsets were studied. In both cases, the data were subdivided so that the symptoms, signs, laboratory findings, and financial costs associated with a specific diagnostic entity-carcinoma of the colon-could be determined.
T
Symptoms None Pain Location Duration Quality Change in bowel habits Bloating Nausea Vomiting Diarrhea Constipation Weight loss Melena Bright red rectal blood Mucus Laboratory Data Hematocrit Stool examination Stool benzidine Hypoalbuminemia Tumor antigen
Signs None Abdominal tenderness Location Quality Abdominal mass Hemorrhoids Fistula or fissure Perianal abscess Hernia Rectal mass Bowel sounds Fever Other Previous X-ray Findings Normal Abnormal Notdone Results notknown Plain film UGI series Gallbladder series IVC Small bowel series Urogram
METHODS
Data Collection Between April 1974 and December 1975, referring physicians were required to fill out computer forms containing information on significant symptoms, signs, and laboratory data pertaining to inpatients and outpatients referred for barium enemas. These forms served as substitutes for the original x-ray requisitions and allowed the physician to describe, in an encodable format, nearly all clinical settings in which a barium enema might be indi-
cated (TABLE I). Thus a physician could readily include information on a patient with a one-month history of mild, intermittent lower left quadrant cramps; an asymptomatic patient with a palpable abdominal mass, moderate anemia, and guaiac-positive stool; and a patient having a routine follow-up examination one year after segmental colectomy for carcinoma. These forms were randomly spot-checked and found
1 From the Department of Radiology, Harvard Medical School and Peter Bent Brigham Hospital, Boston, Mass. Received Sept. 27, 1978; accepted and revision requested Nov. 22;revision received Dec. 15. Supported in part by USPHS grant GM18674 and Career Development Award 5K04-GM00194 (B.J.M). 2 Present address: 812 Cape View Dr., Ft. Myers, Fla. 3 Present address: Department of Radiology, George Washington University Hospital, Washington, D.C. jr
297
DONALD E. GERSON AND OTHERS
298
TABLE
II:
CHARACTERISTICS OF THE POPULATION (N
= 1041)
% of Total Population Sex Age (yr.)
Male Female
46 54
75
22 16 21 23 18
Inpatient Outpatient
53 47
Inpatient/Outpatient
to be accurate and complete on comparison with the patient record. In addition, upon completion of the study, a random check was made of records on patients who had had barium enemas but whose physicians had not completed the questionnaire. In this way! we were able to determine the representativeness of the data; for this purpose we assumed that if the same proportion of abnormal examinations occurred in the group of patients whose physicians completed the form versus those who did not, there was no obvious biased cause for lack of compliance. Physician compliance rates were determined monthly by comparing the number of barium enema examinations performed with the number of computer forms received. The examinations were performed with single-contrast, high-kilovoltage technique, with spot films obtained by the radiologist and overhead films by technicians. Radiologists were required to fill out a second computer form containing their diagnosis and their degree of certainty. All examinations were reviewed by two or more radiologists and the consensus diagnosis incorporated in the radiologist's report was considered the final interpretation. Clinical follow-up ranging from 3 to 24 months was carried out on all patients by a periodic review of the records. Data Analysis
In order to obtain prevalence data on normal, abnormal and equivocal examinations, 1,041 patients were initially examined. All further analyses were then restricted to the subset of the original population examined de novo so that patients undergoing follow-up examinations for known gastrointestinal disease were excluded from consideration. The final group numbered 845 and represented 81 % of the original population. For both populations, barium enemas were designated normal if they were either entirely normal or if they had evidence of only diverticulosis. A study was considered abnormal if any abnormalities were noted, e.g., diverticulitis, carcinoma, polyps, ulcerative and granulomatous colitis, or diverticulosis in conjunction with other abnormalities, etc. A study was considered equivocal if it was felt that no decision could be made as to whether
February 1979
it was normal or abnormal; this occurred most often in cases of poor colonic preparation. The first step in the analysis involved identification of clinical indicators which statistically occurred most often in patients with abnormal examinations. For this purpose, likelihood ratios were used, defined in this context as the frequency of a particular sign, symptom, or physical finding in patients with abnormal enemas, divided by the frequency of that same finding in patients with normal enemas. Likelihood ratios have been used extensively to indicate how various types of diagnostic test results change the likelihood of disease in a particular patient (2-5). These ratios are independent of the prevalence of disease in the group of patients in whom they are derived, and hence can be used directly in other populations. This characteristic contrasts with the relative risk ratio of epidemiology which is prevalence dependent. Indicators with likelihood ratios greater than 1.0 are more likely to be associated with a higher incidence of disease in a particular population than are those with ratios equal to or less than 1.0. In this investigation, the chi square test was used to identify signs, symptoms, or physical findings with likelihood ratios significantly different from 1.0. A disjunctive analysis was performed using all signs, symptoms, and physical findings with likelihood ratios significantly higher than 1.0 (Group A) (6).4 This step assumed that once a patient had at least one significant indicator, clinical practice would never deny him a barium enema. In this context, the disjunctive analysis, which in its general form asks whether one or more finding(s) is(are) present, was used. Thus, the proportion of abnormal barium enemas occurring in patients having one or more sign(s), symptom(s), or physical finding(s) was compared with those having none. For example, the proportion of abnormal barium enemas in patients having abdominal pain or low hematocrit or fever was compared with the diagnostic yield in patients having none of the high likelihood findings. This analysis revealed the proportion of abnormal studies which would have occurred in this population if only selected patients were examined. Because several signs, symptoms, and physical findings traditionally thought useful in the evaluation of patients with gastrointestinal disease did not have likelihood ratios significantly different from 1.0, a second disjunctive analysis was performed using all of the previous signs, symptoms, and physical findings, as well as several traditional ones: weight loss, constipation, diarrhea, change in bowel habits, and bright red rectal blood (Group B). In order to determine the impact equivocal studies might have on the above results, disjunctive analyses were done for two different patient populations: (a) those with normal or abnormal barium enema studies and (b) all patients. In
4 Discriminant analysis is the second most common mathematical technique which uses patient characteristics to group patients according to specific disease. In its traditional form, however, it requires continuous rather than binary data.
THE BARIUM ENEMA
Vol. 130
Diagnostic Radiology
299
this latter analysis, equivocal studies were placed in the abnormal category on the assumption that they might actually be harboring disease. Cost calculations were done using this second patient population.
119(27) 40( 1)
Cost Calculations Total costs were calculated for the entire patient population and for selected subsets (Groups A or B). These assumed a cost for a barium enema of $120. 5 Total costs were then used to calculate the average cost associated with finding a patient with either an abnormal barium enema or with colon cancer in either the entire population or in a subset. We also calculated the additional costs per additional patient found to have either significant gastrointestinal disease of any kind or cancer in particular (marginal costs). All of these costs assume that hospitalization is not required and that barium enemas are generally not followed by other diagnostic tests to confirm the presence of disease.
845 PATIENTS 160
9 13
89 845 Fig. 1. Flow diagram for patients without prior known gastrointestinal disease. There were 845 patients without prior disease; 546 of these (Group A) had statistically significant,indicatorsof d!sease;188 had traditonal nonstatistically significant indicators (Group B); and 111 had neither (Others). The second chance node depicts the distribution of abnormal, equivocal, and normal barium enemas in these 3 groups. The numbers in parentheses indicate those with cancer.
RESULTS
Referring physicians completed computer forms on 66 % of the inpatients and 51 % of the outpatients having barium enemas, for an overall compliance rate of 60 % . Data were available on 1,041 patients. Of these, 845 (81 % ) were patients without known prior disease and 791 of these had unequivocally normal or abnormal examinations. In the entire patient population, there was a relatively equal division between the sexes and between inpatients and outpatients (TABLE II). As expected, the age distribution was skewed toward the elderly, with more than 40% of the patients being 65 years of age or older.
Barium Enema Diagnoses In the entire patient population, 72 % of the examinations were normal, 21 % abnormal, and 7% equivocal. In patients without known disease, 75 % (636) of the examinations were normal, 18% (155) abnormal, and 6% (54) equivocal (Fig. 1). The 155 abnormal studies in this group included carcinoma (29), diverticulitis (12), polyps (42), ulcerative and granulomatous colitis (11), and miscellaneous diagnoses (62); 1 of the 155 patients had two diagnoses. One of the equivocal examinations occurred in a patient ultimately determined to have carcinoma. In the clinical follow-up period of 3-24 months, no additional case of colon carcinoma appeared. All 30 cases of carcinoma were confirmed histologically.
5 Cost analyses were based on observed, averaged examination times, averaged supply costs, known maintenance and lease costs, actual bad debt ratio, indirect costs which included depreciation, and the established cost of professional care. These costs were as follows: technologists' time, $12.69; support personnel, $14.50; film costs, $12.00; supplies, $12.44; maintenance and leases, $5.62; bad debts, $7.21; indirect costs, $26.08; professional costs, including both performance and interpretation, $30.00. This amounts to an aggregate cost of the barium enema of $120.00, including both technical and professional components.
Findings and Their Sensitivity and Associated Likelihood Ratios In the 791 patients with normal or abnormal examinations, the most frequently occurring signs, symptoms, or physical findings included low hematocrit (33 %), abdominal pain (48 %), positive (2+ or greater) stool benzidine (42 % ), abdominal tenderness (31 %), change in bowel habits (25 % ), constipation (22 % ), weight loss (16 % ), and bright red rectal blood (16 % ) (TABLE III). All other indicators
TABLE III: EVALUATIVE CHARACTERISTICS OFCLUES IN PATIENTS WITHOUT KNOWN PRIOR GASTROINTESTINAL DISEASE AND UNEQUIVOCAL BARIUM ENEMA STUDIES (N = 791) Sign, Symptom or Result
Frequency of Occurrence in Entire Population (%)
Rectal mass Fever Hypoalbuminemia Vomiting Abdominal mass Hematocrit
The Barium Enema: Evidence for Proper Utilization 1 Donald E. Gerson, M.D.,2 Ann M. Lewicki, M.D., M.P.H.,3 Barbara J. McNeil, M.D., Ph.D., Herbert L. Abrams, M.D., and Eric Korngold, M.A.
A group of 1,041 patients was studied inanattempt to identify symptoms, signs, or laboratory findings (disease indicators) associated with either a high or lowyield of abnormal barium enemas. A specific search was undertaken for subgroups with one or more statistically significant indicators of large bowel disease. If enemas were performed only forstatistically significant indicators (fever, positive stool benzidine, rectal or abdominal mass, low hematocrit) or indicators of clinical importance (weight loss, constipation, diarrhea, etc.) only 13% of examinations would be eliminated. At the same time, however, 10% of patients with gastrointestinal disease would be missed. INDEX TERMS: Barium enema examination, indications. Colon, diseases. (Colon, examination, 7[5].128). (Colon, routine barium enema, 7[5].1281) Radiology 130:297-301, February 1979 TABLE I: INDICATION FOR BARIUM ENEMA
HE BARIUM ENEMA is so well established and widely used that its utility in diagnostic radiology is rarely questioned. Furthermore, the indications for the examination (rectal bleeding, left lower quadrant pain, constipation, change in bowel habits, etc.) are well known and generally accepted. As a result, there have been few critical evaluations of the relationship of indications to yield (1) and cost effectiveness. The present investigation studied the yield of positive findings in barium enemas of a large group of patients. The major objective was identification of symptoms, signs, and laboratory findings which were correlated with either a high or low yield of abnormal enemas. A secondary objective was determination of the financial implications associated with use of the barium enema as a test for gastrointestinal disease when either the entire initial patient population or selected subsets were studied. In both cases, the data were subdivided so that the symptoms, signs, laboratory findings, and financial costs associated with a specific diagnostic entity-carcinoma of the colon-could be determined.
T
Symptoms None Pain Location Duration Quality Change in bowel habits Bloating Nausea Vomiting Diarrhea Constipation Weight loss Melena Bright red rectal blood Mucus Laboratory Data Hematocrit Stool examination Stool benzidine Hypoalbuminemia Tumor antigen
Signs None Abdominal tenderness Location Quality Abdominal mass Hemorrhoids Fistula or fissure Perianal abscess Hernia Rectal mass Bowel sounds Fever Other Previous X-ray Findings Normal Abnormal Notdone Results notknown Plain film UGI series Gallbladder series IVC Small bowel series Urogram
METHODS
Data Collection Between April 1974 and December 1975, referring physicians were required to fill out computer forms containing information on significant symptoms, signs, and laboratory data pertaining to inpatients and outpatients referred for barium enemas. These forms served as substitutes for the original x-ray requisitions and allowed the physician to describe, in an encodable format, nearly all clinical settings in which a barium enema might be indi-
cated (TABLE I). Thus a physician could readily include information on a patient with a one-month history of mild, intermittent lower left quadrant cramps; an asymptomatic patient with a palpable abdominal mass, moderate anemia, and guaiac-positive stool; and a patient having a routine follow-up examination one year after segmental colectomy for carcinoma. These forms were randomly spot-checked and found
1 From the Department of Radiology, Harvard Medical School and Peter Bent Brigham Hospital, Boston, Mass. Received Sept. 27, 1978; accepted and revision requested Nov. 22;revision received Dec. 15. Supported in part by USPHS grant GM18674 and Career Development Award 5K04-GM00194 (B.J.M). 2 Present address: 812 Cape View Dr., Ft. Myers, Fla. 3 Present address: Department of Radiology, George Washington University Hospital, Washington, D.C. jr
297
DONALD E. GERSON AND OTHERS
298
TABLE
II:
CHARACTERISTICS OF THE POPULATION (N
= 1041)
% of Total Population Sex Age (yr.)
Male Female
46 54
75
22 16 21 23 18
Inpatient Outpatient
53 47
Inpatient/Outpatient
to be accurate and complete on comparison with the patient record. In addition, upon completion of the study, a random check was made of records on patients who had had barium enemas but whose physicians had not completed the questionnaire. In this way! we were able to determine the representativeness of the data; for this purpose we assumed that if the same proportion of abnormal examinations occurred in the group of patients whose physicians completed the form versus those who did not, there was no obvious biased cause for lack of compliance. Physician compliance rates were determined monthly by comparing the number of barium enema examinations performed with the number of computer forms received. The examinations were performed with single-contrast, high-kilovoltage technique, with spot films obtained by the radiologist and overhead films by technicians. Radiologists were required to fill out a second computer form containing their diagnosis and their degree of certainty. All examinations were reviewed by two or more radiologists and the consensus diagnosis incorporated in the radiologist's report was considered the final interpretation. Clinical follow-up ranging from 3 to 24 months was carried out on all patients by a periodic review of the records. Data Analysis
In order to obtain prevalence data on normal, abnormal and equivocal examinations, 1,041 patients were initially examined. All further analyses were then restricted to the subset of the original population examined de novo so that patients undergoing follow-up examinations for known gastrointestinal disease were excluded from consideration. The final group numbered 845 and represented 81 % of the original population. For both populations, barium enemas were designated normal if they were either entirely normal or if they had evidence of only diverticulosis. A study was considered abnormal if any abnormalities were noted, e.g., diverticulitis, carcinoma, polyps, ulcerative and granulomatous colitis, or diverticulosis in conjunction with other abnormalities, etc. A study was considered equivocal if it was felt that no decision could be made as to whether
February 1979
it was normal or abnormal; this occurred most often in cases of poor colonic preparation. The first step in the analysis involved identification of clinical indicators which statistically occurred most often in patients with abnormal examinations. For this purpose, likelihood ratios were used, defined in this context as the frequency of a particular sign, symptom, or physical finding in patients with abnormal enemas, divided by the frequency of that same finding in patients with normal enemas. Likelihood ratios have been used extensively to indicate how various types of diagnostic test results change the likelihood of disease in a particular patient (2-5). These ratios are independent of the prevalence of disease in the group of patients in whom they are derived, and hence can be used directly in other populations. This characteristic contrasts with the relative risk ratio of epidemiology which is prevalence dependent. Indicators with likelihood ratios greater than 1.0 are more likely to be associated with a higher incidence of disease in a particular population than are those with ratios equal to or less than 1.0. In this investigation, the chi square test was used to identify signs, symptoms, or physical findings with likelihood ratios significantly different from 1.0. A disjunctive analysis was performed using all signs, symptoms, and physical findings with likelihood ratios significantly higher than 1.0 (Group A) (6).4 This step assumed that once a patient had at least one significant indicator, clinical practice would never deny him a barium enema. In this context, the disjunctive analysis, which in its general form asks whether one or more finding(s) is(are) present, was used. Thus, the proportion of abnormal barium enemas occurring in patients having one or more sign(s), symptom(s), or physical finding(s) was compared with those having none. For example, the proportion of abnormal barium enemas in patients having abdominal pain or low hematocrit or fever was compared with the diagnostic yield in patients having none of the high likelihood findings. This analysis revealed the proportion of abnormal studies which would have occurred in this population if only selected patients were examined. Because several signs, symptoms, and physical findings traditionally thought useful in the evaluation of patients with gastrointestinal disease did not have likelihood ratios significantly different from 1.0, a second disjunctive analysis was performed using all of the previous signs, symptoms, and physical findings, as well as several traditional ones: weight loss, constipation, diarrhea, change in bowel habits, and bright red rectal blood (Group B). In order to determine the impact equivocal studies might have on the above results, disjunctive analyses were done for two different patient populations: (a) those with normal or abnormal barium enema studies and (b) all patients. In
4 Discriminant analysis is the second most common mathematical technique which uses patient characteristics to group patients according to specific disease. In its traditional form, however, it requires continuous rather than binary data.
THE BARIUM ENEMA
Vol. 130
Diagnostic Radiology
299
this latter analysis, equivocal studies were placed in the abnormal category on the assumption that they might actually be harboring disease. Cost calculations were done using this second patient population.
119(27) 40( 1)
Cost Calculations Total costs were calculated for the entire patient population and for selected subsets (Groups A or B). These assumed a cost for a barium enema of $120. 5 Total costs were then used to calculate the average cost associated with finding a patient with either an abnormal barium enema or with colon cancer in either the entire population or in a subset. We also calculated the additional costs per additional patient found to have either significant gastrointestinal disease of any kind or cancer in particular (marginal costs). All of these costs assume that hospitalization is not required and that barium enemas are generally not followed by other diagnostic tests to confirm the presence of disease.
845 PATIENTS 160
9 13
89 845 Fig. 1. Flow diagram for patients without prior known gastrointestinal disease. There were 845 patients without prior disease; 546 of these (Group A) had statistically significant,indicatorsof d!sease;188 had traditonal nonstatistically significant indicators (Group B); and 111 had neither (Others). The second chance node depicts the distribution of abnormal, equivocal, and normal barium enemas in these 3 groups. The numbers in parentheses indicate those with cancer.
RESULTS
Referring physicians completed computer forms on 66 % of the inpatients and 51 % of the outpatients having barium enemas, for an overall compliance rate of 60 % . Data were available on 1,041 patients. Of these, 845 (81 % ) were patients without known prior disease and 791 of these had unequivocally normal or abnormal examinations. In the entire patient population, there was a relatively equal division between the sexes and between inpatients and outpatients (TABLE II). As expected, the age distribution was skewed toward the elderly, with more than 40% of the patients being 65 years of age or older.
Barium Enema Diagnoses In the entire patient population, 72 % of the examinations were normal, 21 % abnormal, and 7% equivocal. In patients without known disease, 75 % (636) of the examinations were normal, 18% (155) abnormal, and 6% (54) equivocal (Fig. 1). The 155 abnormal studies in this group included carcinoma (29), diverticulitis (12), polyps (42), ulcerative and granulomatous colitis (11), and miscellaneous diagnoses (62); 1 of the 155 patients had two diagnoses. One of the equivocal examinations occurred in a patient ultimately determined to have carcinoma. In the clinical follow-up period of 3-24 months, no additional case of colon carcinoma appeared. All 30 cases of carcinoma were confirmed histologically.
5 Cost analyses were based on observed, averaged examination times, averaged supply costs, known maintenance and lease costs, actual bad debt ratio, indirect costs which included depreciation, and the established cost of professional care. These costs were as follows: technologists' time, $12.69; support personnel, $14.50; film costs, $12.00; supplies, $12.44; maintenance and leases, $5.62; bad debts, $7.21; indirect costs, $26.08; professional costs, including both performance and interpretation, $30.00. This amounts to an aggregate cost of the barium enema of $120.00, including both technical and professional components.
Findings and Their Sensitivity and Associated Likelihood Ratios In the 791 patients with normal or abnormal examinations, the most frequently occurring signs, symptoms, or physical findings included low hematocrit (33 %), abdominal pain (48 %), positive (2+ or greater) stool benzidine (42 % ), abdominal tenderness (31 %), change in bowel habits (25 % ), constipation (22 % ), weight loss (16 % ), and bright red rectal blood (16 % ) (TABLE III). All other indicators
TABLE III: EVALUATIVE CHARACTERISTICS OFCLUES IN PATIENTS WITHOUT KNOWN PRIOR GASTROINTESTINAL DISEASE AND UNEQUIVOCAL BARIUM ENEMA STUDIES (N = 791) Sign, Symptom or Result
Frequency of Occurrence in Entire Population (%)
Rectal mass Fever Hypoalbuminemia Vomiting Abdominal mass Hematocrit
